from drought to death: the ecohydrology and physiology of...
TRANSCRIPT
From Drought to Death:
The Ecohydrology and Physiology of
Sudden Aspen Decline
Leander D.L. Anderegg1,
W.R.L. Anderegg2, J.A. Berry3, C.B. Field3,4
CA Forest Pest Council Meeting
11/21/2013
1University of Washington 2Princeton University 3Carnegie Institute for Science 4Stanford University
wikipedia.org
Populus tremuloides
• Defined by
– Rapid onset and regional scale
– No single inciting agent
– Lack of regeneration
– Often accompanied by root mortality
Sudden Aspen Decline
Precipitation Deficit
Soil Moisture
Deficit
Plant Water Stress
Physiological Damage
Plant Death
Feedbacks
Physiological
Threshold
Adapted from LDL Anderegg et al. 2013 Tree Phys
Physiology of Mortality
Ecohydrological Context
Precipitation Deficit
Soil Moisture
Deficit
Plant Water Stress
Physiological Damage
Plant Death
Feedbacks
Physiological
Threshold
Ecohydrological Context
Why did 2002 stress aspens out?
• What water sources do aspens use?
• What were the characteristics of the 2002 drought that made aspens run dry?
-150
-130
-110
-90
-70
-50
-30
-10
-18 -16 -14 -12 -10 -8 -6 -4 -2
del 18O
δ D
groung water
rain
snow
LMWL
Evaporation
Stable H2O Isotopes: a primer
ground water
Aspen xylem isotopes during growing season (May-July) drought
LDL Anderegg et al. 2013, GCB
What did the 2002 drought look like climatically?
• Look in climate record for: Extreme conditions or unique combination of conditions that led to dry shallow soil
Max moisture deficit
Min 10cm soil moisture
LDL Anderegg et al. 2013, GCB
10
cm S
oil
Mo
istu
re
Mo
istu
re D
efic
it
Precipitation Deficit
Soil Moisture
Deficit
Plant Water Stress
Physiological Damage
Plant Death
Feedbacks
Physiological
Threshold
Adapted from LDL Anderegg et al. 2013 Tree Phys
Physiology of Mortality
Ecohydrological Context
Long, hot growing season - Drove high evaporative
demand - Dried out shallow soil
moisture
Aspens are tied to shallow soil moisture, even during drought
Drought trees lose conductivity
Dying trees have lost conductivity
WRL Anderegg et al. 2012 PNAS
Branch Root
Co
ntr
ol
Co
ntr
ol
Dro
ugh
t
Dro
ugh
t
WRL Anderegg et al. 2013 GCB
Conductance = Predictor of Mortality
Nagelkerke R2 = 0.64, P < 10-6
WRL Anderegg et al. 2013 GCB
Potential Feedbacks:
1) Long term growth declines
2) Increased water stress (via root mortality)
3) Increased xylem vulnerability
4) Decreased pathogen resistance?
How do you get lagged mortality?
Precipitation Deficit
Soil Moisture
Deficit
Plant Water Stress
Physiological Damage
Plant Death
Feedbacks
Physiology of Mortality
Ecohydrological Context
Long, hot growing season - Drives high evaporative
demand - Dries out shallow soil
moisture
Aspens are tied to shallow soil moisture, even during drought
Acute water stress cause xylem cavitation
Cavitation fatigue increases vulnerability
Conductance decreases, whole tree coordination and function disrupted
Acknowledgements
Collaborators: John Abatzoglou Lenka Plavcova Uwe Hacke Ali Hausladen Duncan Smith John Sperry Funded by: Stanford VPUE undergraduate research grants, Mel
Lane Center for the American West, Carnegie Department of Global Ecology, NSF DDIGG, Phi Beta Kappa Norther CA chapter, DOE SCGF, Morrison Institute, Stanford Biology SCORE grant
Thanks to: Lizzie Callaway
Maggie Love & Mike Anderegg
Jessi Love-Nichols
Brandon Blakeley
Kim Pham
Todd Dawson
Paul Brooks & Chris Wong, Center for Stable Isotope Biogeochemistry, Berkeley
Jasper Ridge Biological Preserve
What did the 2002 drought look like climatically?
• Look in climate record for: Extreme conditions or unique combination of conditions that led to dry shallow soil
Bad snow year
Not worst summer
Early melt
Hot Spring-Summer
LDL Anderegg et al. 2013, GCB
Explaining Spatial Variation In Mortality
R2 = 0.32, p = 0.005
1) 2002 Summer Temp
2) 2002 10cm soil moisture
National Forest Service Flyover map (2008)
SAD and Drought
• Low elevations and southern aspects
• Negative density dependance
• Region wide simultaneous onset
Worrall et al. 2008
Precipitation Deficit
Soil Moisture
Deficit
Plant Water Stress
Physiological Damage
Plant Death
Community: Hydraulic Redistribution Water partitioning Competition
Species: Rooting depth/plasticity Drought adaptation strategy Phenology
Evapotranspiration: Timing Magnitude Growing season length Depth of extraction
Temporal vulnerability of processes & organs : Nutrient uptake Growth and repair Cold hardening Carbon allocation
Feedbacks: Root mortality Decreased growth Cavitation fatigue Nutrient limitation Weakened defenses
1 2 3a
3b
4
Physiological
Threshold
Climate Precipitation • Timing • Form • Sequence Evaporation • Temp • RH • Wind • Radiation
Edaphic Features Topography Soil Properties
Physiological traits: Hydraulic architecture Carbon balance Strength of stomatal regulation Carbon allocation strategy